Re: Bootstrapping Debian GNU/Linux distribution on SuperH

[NIIBE Yutaka <gniibe@m17n.org>]

NIIBE Yutaka wrote:
 > However, according to Hitachi, the ABI is different between SH3 and
 > SH4.  Please check out programming manuals of SH3 and SH4.
 > Instruction set are backward compatible.  However, some instructions
 > are allowed in delay-slot for SH3 but not for SH4.  I mean, if someone
 > tunes a program for SH3 pipeline, it may not work on SH4.  It's easy
 > to write such program, if people use assembler.  Current GCC does not
 > emit such a code (this is the reason why almost all code work fine).
 > But it's free to do so in future GCC, because the definition of ABI is
 > different.

This is just a POTENTIAL issue.

I forgot to mention *important* CURRENT problem.

The executable is almost compatible, that's true.  The object and/or
shared library are *not* compatible, because the ABI of calling
convention is different.  Hitachi defines that ABI.

When structure is passed to the function with the argument, the order
is different between SH3 and SH4.  The object and/or library compiled
by -m3 and -m4 should _not_ be linked, or else, it crashes runtime.

In short, if you only have SH3 executable and shared libraries, that's
fine (not guaranteed in future, though).  However, you cannot mix SH3
binaries with SH4's, as it's not compatible.
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